THE PRIMARY STRUCTURE OF THE PHOSPHATIDYLCHOLINE-EXCHANGE PROTEIN FROM BOVINE LIVER - ISOLATION AND CHARACTERIZATION OF THE STAPHYLOCOCCAL PROTEASE PEPTIDES AND THE AMINO-ACID-SEQUENCE OF THE N-TERMINAL HALF (RESIDUES 1-122)

Abstract

The phosphatidylcholine exchange protein from bovine liver consists of a single polypeptide chain and has a blocked N terminus. The protein contains an estimated 244 amino acid residues in accordance with a determined MW of 28,000. The protease from mouse submaxillaris gland cleaved the citraconylated and S-carboxymethylated derivative of the exchange protein at one specific site (Arg14-Glu15) close to the N terminus. Analysis of the 2 resulting peptides showed that N-acetyl-methionine was the N-terminal residue and gave the sequence of the first 41 residues. The modified protein was fragmented with the protease from S. aureus. The peptides isolated represented 88% of the protein; their sequences were determined by manual and automated Edman degradation. Alignment of a number of these peptides gave the complete sequence of the N-terminal half up to position 122.